It would be nice if -a did everything imaginable to make the destination be like the source, but for some reason it doesn't, and now it's too late to change it.
So there should be a new argument, perhaps --all) that means -aHAX and furthermore means that if some other metadata comes along that needs to be copied, it will be subsumed under this same all-encompassing --all option argument.

Thanks. I'm considering adding the --all option.
Note that you can decide that you want your local rsync to treat -a as -aHAX, or add your own --all option via a popt alias in either the global file (/etc/popt) or your local file (~/.popt). Here's the --all option:
rsync alias --all -aHAX
And here's an override of -a:
rsync alias -a -aHAX